This invention relates to the head actuator assembly for a rotating disk system for storing computer data on magnetic media. Such systems are sometimes known as hard disk drives. More particularly, the invention relates to the assembly of load beams for supporting magnetic recording heads adjacent to the disk surfaces.
Hard disk drives are essentially universally used for computers. In recent years, the disk drives have steadily decreased in size while at the same time increasing in storage capacity. Miniaturization of the magnetic memory disk data storage systems has presented significant challenges to the designer to provide systems that can be economically manufactured in large numbers with a high degree of reliability and maximum data storage capacity. The present invention meets at least some of such challenges for a generation of storage disks only 1.8 inches (4.5 cm.) in diameter.
An exemplary disk drive has a pair of flat circular disks spaced a short distance apart and rotating about a common axis. The surfaces of the disks are coated with a magnetic recording medium. Data are stored in the thin layers of magnetic medium by magnetizing small areas of the media. Typically, the stored data is divided into "tracks" that are concentric rings on the disk surface. A magnetic read/write head is positioned adjacent to each face of the disk. As the disk is rotated beneath the read/write head, it can magnetize the magnetic medium in the track, thereby writing onto the track, or it can read the magnetic pattern stored along the track for retrieving data. Each region along the track in which a bit of data is stored has become extremely small as disk dimensions have shrunk and the demands for higher disk capacity have been met. Furthermore, the width of the tracks in the radial direction has become smaller and smaller.
The magnetic read/write heads for a disk drive are supported at the outboard ends of what are known as load beams. The read/write head is in a "slider" on the end of the load beam. Each load beam is designed to press the slider toward the surface of the disk. When the disk is not rotating, the slider is pressed into contact with the disk surface. When the disk rotates, a film of air swept along by the rotating disk provides an air bearing between the slider and disk surface. The slider and read/write head "fly" or float on the air bearing an extremely small distance from the disk surface.
The four load beams (for an embodiment with two disks) are mounted together in a head actuator assembly which is pivotably mounted beside the rotating disks. When the head actuator assembly is pivoted, the outboard ends of the load beams sweep across the face of the disks for moving the sliders and read/write heads generally radially so that the read/write head is over a selected recording track. In this mounting arrangement, the length of the load beam is approximately tangential to the tracks.
An important feature of the head actuator assembly is that the sliders on the load beams are in alignment. In other words, it is important that the two sliders on opposite faces of the disk be at substantially the same radial position at all times.
Assume, for example, that one slider is at a shorter radial distance while the other is at a greater radial distance. When the two sliders are pivoted toward the axis of the disk, they will approach the spindle on which the disks are mounted. The one read/write head can record data closer to the spindle than the other head. On the other hand, when the head actuator assembly is pivoted toward the circumference of the disk, the slider that is radially further outward can record data closer to the circumference of the disk than the head which is out of alignment.
This means that potential inner tracks cannot be used on one face of the disk because one read/write head cannot approach the spindle as closely as the other head. Similarly, some tracks near the circumference will be lost on the opposite face of the disk where one of the heads cannot reach. As higher storage capacity is sought, it becomes more important to achieve closer alignment of the heads in the head actuator assembly. One cannot afford to lose the use of any available data tracks. Thus, means for readily obtaining and maintaining alignment of the sliders in a head actuator assembly is highly desirable.
A previous technique for forming a head actuator assembly having a plurality of load beams is described and illustrated in U.S. Pat. No. 4,829,395. In this assembly, a number of load beams are connected to a block by "ball staking." Part of the assembly has a boss with a passage having a narrow region. The boss is inserted in a mating hole and a ball is pressed through the passage. The ball has a larger diameter than the narrow region of the passage and swages the boss outwardly, thereby staking the parts together. Such a ball staking technique is also used in another embodiment of prior head assembly where the head actuator assembly has what amounts to an E-shaped block. Several load beams are ball staked to arms of the E-shaped block.
The ball staking essentially permanently attaches the load beam to the supporting block. This makes rework difficult in the event one of the load beams and the structure connected to it has a defect and needs to be replaced or removed for repair. Furthermore, when a ball staked part is removed, it becomes difficult to reattach and cracking of the metal may actually make it impossible. Thus, parts from such assembly may not be reusable. It would therefore be desirable to have load beam assemblies that could be disassembled for ease of repair and replacement.
It would also be desirable to have an assembly fixture which facilitates assembly and alignment of the load beam assemblies, and preferably, one that may have additional uses during the manufacture of a disk drive.